Method of producing porous metal-carbon materials

ABSTRACT

A method for creating a metal-carbon composite. In one embodiment, the method includes the steps of providing a polymer Schiff base transition metal film complex precursor film having a chemical structure of the formula [M(Schiff)] n  and a recurring unit and a transition metal selected from the group consisting of nickel, palladium, platinum, cobalt, copper, iron; Schiff is a tetradentate Schiff base ligand selected from the group consisting of Salen (residue of bis(salicylaldehyde)-ethylenediamine), Saltmen (residue of bis(salicylaldehyde)-tetramethylethylenediamine, Salphen (residue of bis-(salicylaldehyde)-o-phenylenediamine), a substituent in a Schiff base is selected from the group consisting of H—, and carbon-containing substituents, preferably CH 3 —, C 2 H 5 —, CH 3 O—, C 2 H 5 O—, and Y is a bridge in a Schiff base depositing the polymer Schiff base transition metal precursor film onto a support substrate; and heating the polymer Schiff base transition metal complex precursor film and support substrate in a furnace in an inert atmosphere.

RELATED APPLICATIONS

This application is a reissue application of U.S. Pat. No. 9,653,736,filed Aug. 13, 2015 and issued May 16, 2017, which claims priority toU.S. Provisional Application 62/039,010, filed Aug. 19, 2014, the entirecontents of which are herein incorporated by reference in theirentirety.

FIELD OF INVENTION

This invention relates to methods of producing porous metal-carbonmaterials with high electric conductivity and high specific surface areawith controllable pore size distribution.

BACKGROUND OF THE INVENTION

Porous carbon materials (CMs) with high specific surface area are widelyused for many electrochemical, catalytic, and adsorption applications.The preparation of such materials usually involves two steps: 1)formation of carbon via carbonization of precursor material; 2)activation of carbon in order to enhance its surface area.

Porous CMs may be produced via carbonization of naturally occurring rawmaterials, such as wood, petroleum pitch, peat, and other sources ofhigh carbon content. A major advantage of CMs prepared from naturallyoccurring raw materials is their relatively low cost. At the same time,such CMs contain large amounts of impurities such as sulfur, nitrogen,phosphor and metal salts, which initially reside in the precursormaterial. Such impurities may introduce undesirable side reactions whencarbon material is employed, for example, in energy storage devices suchas lithium-ion batteries, fuel cells or double layer capacitors. Theseside reactions may deteriorate the structure and lower the performanceof the device.

Porous CMs may also be formed by carbonizing synthetic materials of highcarbon content, for example polymers, at very high temperatures in anon-oxidative (inert) atmosphere, for example nitrogen, argon, orhelium. The most widely-employed synthetic polymer precursor for makingCMs is polyacrylonitrile. Other precursors such as phenolic resin andpolyacetylenes may also be used. The disadvantage of CMs made fromsynthetic polymers is that these CMs have a very low specific surfacearea.

To enhance the surface area of CMs, activation is always performed afterthe carbonization process. The physical activation is accomplished withsteam, carbon monoxide (CO), carbon dioxide (CO₂), and CO₂-containinggases. The chemical activation agents are ZnCl₂, H₂SO₄, H₃PO₄, NaOH,LiOH, KOH, N_(x)O_(y) [x=1-2, y=1-3], Cl₂ and other halogens. Activationprovides for enhanced surface area of CMs, but it can introduce defectsor completely destroy a formed carbon body.

To be useful for electrochemical and catalytic applications, theresulting high surface area CM should have the following properties:nano- or molecular-level organization of carbon structure, withstructural elements (carbon fragments) ranging in size from 1 nm(molecular dimensions) to 10-100 nm (nano dimensions); regulateddistribution of structural elements (carbon fragments), that can beadjusted to suit the material application; narrow pore sizedistribution; high electronic conductivity; high chemical stability andmechanical strength; and low cost.

A major problem in many carbon material applications is a relativelyhigh internal resistance of CMs, which can be lowered through use ofmetal-carbon materials (MCMs). Uniform imbedding of metal atoms in theform of, for example, nano-sized particles or clusters into the porouscarbon structure also improves and expands the catalytic properties ofthe discussed MCMs.

Various fabrication techniques for preparation of metal-carbon materialshave been disclosed. One of the methods of fabrication implies thermalcatalytic decomposition of hydrocarbons in the microporous metal matrix.One method describes the synthesis of MCM by thermal chemical vapordeposition of ethane in the presence of hydrogen at 660° C. on sinteredmetal fiber filters of nickel and Ni-containing alloys.

Another technique implies impregnation of high surface area porouscarbon with metal precursors (metal salts or metal complexes) followedby their reduction to pure metals or metal oxides. For example, onemethod describes the approach where the carbon fiber material is dippedinto an aqueous solution of ruthenium chloride followed by thermaldecomposition to ruthenium oxide formed in the pores of the carbonfibers.

The majority of fabricated metal-carbon materials have metal-carbonglobules or fibers of different pre-defined dimensions, but the relativedistribution of globules (or fibers) is chaotic and difficult toregulate. This difficulty in regulation prevents the preparation of MCMswith predefined and controllable properties that suit the materialapplication, which in turn limits the widespread use of these materials.

The present invention addresses this need.

SUMMARY OF THE INVENTION

One aspect of the present invention is a method for producing a porousmetal-carbon material (MCM) having high electronic conductivity, a highspecific surface area, controllable elementary composition, a uniformdistribution of metal atoms inside the MCM, and controllable pore sizedistribution, based on the requirements of specific applications.

In one embodiment, a method for producing a porous metal-carbon materialincludes carbonizing a polymer grown on a support; the polymer being apolymer Schiff base transition metal complex. In one embodiment,carbonizing is accomplished by heating the support-mounted polymer undera non-oxidative (inert) atmosphere at a temperature ranging from 500° C.to 750° C. for a time period sufficient to form a metal-carbon materialon the support.

In various embodiments, metal-carbon composite materials of thisinvention are made from polymer Schiff base transition metal complexes(hereinafter referred to as poly [M(Schiff)], where M is a transitionmetal and Schiff is a tetradentate Schiff base ligand) grown byoxidative electrochemical polymerization of corresponding square-planarmonomer complexes on the surface of an inert electrically conductingsupport.

In other embodiments, poly[M(Schiff)] polymers have high carbon content,metal atoms evenly distributed throughout the polymer structure, highsurface area, and uniform distribution of structural elements along thesurface of the support. Structural elements of poly[M(Schiff)] polymersare individual stacks arranged perpendicular to the support surface.Each stack is formed from monomer square-planar fragments [M(Schiff)]via donor-acceptor interactions between a metal center of one monomerfragment and a phenyl ring of a ligand that is part of another monomerfragment. The length and diameter of the stacks and the distance betweenthe stacks are pre-defined by the monomer composition and polymerizationconditions (polymerization potential, polymerization regime, supportingelectrolyte, and solvent).

Polymer Schiff base transition metal complexes are thermally stable attemperatures below 370° C. When these polymers are heated at highertemperatures in a non-oxidative (inert) atmosphere, the carbonization ofthe polymers begins. The carbonization includes the decomposition theorganic portion of the polymer accompanied by evolving hydrogen, oxygenand nitrogen. The result of a complete carbonization of apoly[M(Schiff)] polymer is the formation of a metal-carbon material.

The geometry of the resulting metal-carbon material closely resemblesthe geometry of the initial polymer. In the process of carbonization,polymer stacks turn into pillar-like elements consisting of carbon andmetal atoms, and a MCM composed of structural elements having steric andgeometrical resemblance to the polymer stacks is formed. The diameter ofsaid elements is from 1 to 1.5 nanometers and is determined by thediameter of stacks in the precursor polymer. The length of said elementsis up to 50 micrometers and determined by the thickness of the precursorpolymer film. The elements are spaced at a distance from 0.2 to 10nanometers from each other, which corresponds to the initialdistribution of polymer stacks along the surface of the support. Theregular spacing between pillar-like elements makes the producedmetal-carbon material highly porous, with uniform pore size distributionin the nanopore region. The preservation of the initial polymer geometryin the resulting MCM is provided by the carbonization of thesupport-mounted poly[M(Schiff)] polymer, the support being the supportused for growing the polymer.

The result of the present invention is the formation of the metal-carbonmaterial on the support, with said metal-carbon material having thefollowing properties: specific electrochemically-active surface areabetween 50 m²/g and 2,500 m²/g; a carbon content from 50 to 85 weightpercent; a metal-to-carbon weight ratio from 0.2 to 1.0; a controllableregular structure comprised of pillar-like elements having a diameter of1 to 1.5 nanometers, length up to 50 micrometers, placed at a distancefrom 0.2 to 10 nanometers from each other along the support surface; anda uniform distribution of metal clusters with a chemical formula MC_(n),wherein M is a metal atom, C is a carbon atom, and (n) is a number from0.5 to 6 inside the metal-carbon material.

The presence of metal atoms evenly distributed throughout themetal-carbon material results in high electronic conductivity of theMCM.

These and other objects and features of the present invention will bemore apparent from a detailed description that follows.

DETAILED DESCRIPTION OF THE INVENTION

Polymer Schiff base transition metal complexes, precursors used to makemetal-carbon materials of this invention, have a chemical structurecharacterized by the formula [M(Schiff)]_(n) and the recurring unit ofthe following structure:

wherein n is an integer between 2 and 50,000; M is a transition metalselected from the group consisting of nickel, palladium, platinum,cobalt, copper, iron; Schiff is a tetradentate Schiff base ligandselected from the group consisting of Salen (residue ofbis(salicylaldehyde)-ethylenediamine), Saltmen (residue ofbis(salicylaldehyde)-tetramethylethylenediamine, Salphen (residue ofbis-(salicylaldehyde)-o-phenylenediamine), R is a substituent in aSchiff base selected from the group consisting of H—, andcarbon-containing substituents, preferably CH₃—, C₂H₅—, CH₃O—, C₂H₅O—,and Y is a bridge in a Schiff base and has the following structure:

—CH₂—CH₂— in Salen

in Saltmen

in Salphen

Structural elements of the polymer Schiff base transition metalcomplexes (poly[M(Schiff)]) are individual stacks arranged perpendicularto the support surface. Each stack is formed from monomer square-planarfragments [M(Schiff)] via donor-acceptor interactions between a metalcenter of one monomer fragment and a phenyl ring of a ligand that ispart of another monomer fragment. Charge transfer in polymer Schiff basetransition metal complexes occurs via “electron hopping” between metalcenters with different oxidation states (redox conductivity). Oxidationor reduction of polymer metal complexes associated with the change inthe oxidation states of metal centers is accompanied by ingress/egressof charge-compensating counter-ions of electrolyte solution into/out ofthe polymer film to maintain overall electrical neutrality of thesystem.

Poly[M(Schiff)] polymers structured at the molecular level, i.e. withuniform controllable distribution of structural elements (stacks) on thesupport surface, can be grown by using different strategies of theoxidative electrochemical polymerization of Schiff base transition metalcomplexes. These polymers have high carbon content, high surface area,and metal atoms evenly distributed throughout the polymer structure.

The method of preparing the metal-carbon material of the presentinvention comprises the carbonization of a polymer grown on a support,with said polymer being a polymer Schiff base transition metal complex,accomplished by heating the support-mounted polymer under anon-oxidative (inert) atmosphere at an elevated temperature.

The precursor polymer for producing the metal-carbon material ispreferably in the form of a polymer film grown on a support by oxidativeelectrochemical polymerization. The polymer film thickness is limited bythe distance, at which the initial controllable distribution ofstructural elements (stacks) is preserved (usually, up to 50micrometers).

The support is selected from the group consisting of electronicallyconductive materials, such as carbon, including glassy carbon, carbonfibers, carbon fibrils, and other carbon materials, carbon materialswith metal coatings, and metals, more preferably metalselectrochemically inert at the potentials of the polymerization.

The precursor polymer for producing the metal-carbon material ispreferably in the form of a polymer structured at the molecular level,with required elemental composition and pre-defined distribution ofstructural elements (stacks) on the support surface, based on therequirements of the MCM application.

The support-mounted precursor polymer is then transferred to acontainer, preferably a tube furnace, that is filled with anon-oxidizing atmosphere including nitrogen, argon, or helium, andheated to elevated temperatures ranging from 500° C. to 750° C.,preferably from 550° C. to 650° C., and more preferably from 580° C. to620° C. Upon reaching the required temperature, the heating is conductedat this temperature for the time period sufficient to fully accomplishthe carbonization of the precursor polymer; typically, between 1 and 4hours, and preferably between 2 and 3 hours.

“Carbonization” is defined herein as increasing the carbon content inthe precursor material by heating it in a non-oxidizing environment toelevated temperatures, during which hydrogen, oxygen and nitrogen areevolved. The reaction product after fully accomplished carbonization ofa polymer Schiff base transition metal complex is a metal-carbonmaterial.

The geometry of the resulting metal-carbon material closely resemblesthe geometry of the initial polymer. In the process of carbonization,polymer stacks turn into pillar-like elements consisting of carbon andmetal atoms, and a MCM composed of structural elements having steric andgeometrical resemblance to the polymer stacks is formed. The diameter ofthe elements is from 1 to 1.5 nanometers and is determined by thediameter of stacks in the precursor polymer. The length of the elementsis up to 50 micrometers and is determined by the thickness of theprecursor polymer film. The elements are spaced at a distance from 0.2to 10 nanometers from each other, which corresponds to the initialdistribution of polymer stacks along the surface of the support. Theregular spacing between pillar-like elements makes the resultingmetal-carbon material highly porous, with uniform pore size distributionin the nanopore region. The preservation of the initial polymer geometryin the resulting MCM is provided by performing carbonization of thesupport-mounted poly[M(Schiff)] polymer, the support being the supportused for growing the polymer.

The resulting metal-carbon material has a high carbon content from 50 to85 weight percent and a metal-to-carbon weight ratio from 0.2 to 1.0, asdetermined by the chemical composition of the precursor polymer. Themetal atoms are uniformly distributed inside the composite material andexist in the form of metal clusters with a chemical formula MC_(n),wherein M is a metal atom, C is a carbon atom, and (n) is a number from0.5 to 6. The presence of dispersed metal atoms in the structure of theMCM results in higher electronic conductivity of the metal-carbonmaterial than that of conventional porous CMs.

The resulting metal-carbon composite material can have a specificelectrochemically-active surface area between 50 m²/g and 2,500 m²/g,without any additional activation. “Electrochemically-active surfacearea” is defined herein as an internal surface area accessible for ionsof the supporting electrolyte in an electrochemical experiment. Thevalue of a specific electrochemically-active surface area is calculatedusing the value of specific double-layer capacity determined by cyclicvoltammetry investigation of the MCM sample in the acetonitrile solutioncontaining 0.1 mol/L of tetraethylammonium tetrafluoroborate.

The parameters of the process of producing the metal-carbon material ofthis invention significantly affect the properties of the final product.

The carbonization temperature affects the carbon content and the valueof specific electrochemically-active surface area in the MCM. Theprocess performed at temperatures that are lower than required for theeffective carbonization of a given polymer results in the formation ofan under-carbonized MCM. Such under-carbonized material retains aportion of hydrogen, oxygen, and nitrogen atoms, which lowers theultimate carbon yield. The under-carbonized material also retains aportion of the insulating polymer that has already lost redoxconductivity but has not yet acquired electronic conductivity. As aresult, the final MCM has relatively low electronic conductivity anddecreased value of specific electrochemically-active surface area.Heating the precursor polymer to temperatures that are higher thanrequired for the effective carbonization of a given polymer results inagglomeration of individual structural elements, which results in lowporosity of the final metal-carbon material.

The carbonization process performed at a required temperature for aninsufficient time period also leads to the formation of under-carbonizedMCM with lower carbon content and decreased specificelectrochemically-active surface area.

The porosity of the final metal-carbon material also depends on theprecursor polymer properties. As discussed above, the properties ofpoly[M(Schiff)] polymers can be effectively controlled by altering theconditions of the polymerization, such as monomer structure,polymerization regime, supporting electrolyte, and solvent.

The metal-carbon materials of the present invention can be utilized asbase or main materials for catalytic and other applications that demanda high surface area with a controlled porosity.

Other areas of the application of metal-carbon materials are energyproduction and energy storage, such as electrodes for fuel cells, doublelayer capacitors, lithium-ion, and lithium-polymer batteries.

Ultimately, the properties of the metal-carbon materials of the presentinvention can be effectively controlled based on the requirements ofspecific applications.

The selectivity of metal-carbon materials of the present invention incatalytic applications can be provided by altering a metal center in theprecursor polymer. For example, nickel-containing MCMs will be mosteffective as catalysts for hydrogenation processes, whereaspalladium-containing MCMs will effectively catalyze the oxidation ofmethanol. The accessibility of metal catalytic centers for substratemolecules and high rates of diffusion of substrates and reactionproducts inside the solid-state catalyst can be ensured by usingmetal-carbon materials with large pores and relatively low specificelectrochemically-active surface area.

The metal-carbon materials with high specific electrochemically-activesurface area are most effective for applications in energy-producing andenergy-storage devices that normally require high porosity and highspecific surface area of electrode material.

The following examples illustrate the present invention, but should notbe construed as limiting the invention:

EXAMPLES Example 1

A polymer film with a formula poly[Cu(CH₃O-Salen)] and a recurring unitwas employed to prepare a metal-carbon material. The polymer film havingthe thickness of 0.8 micrometers and mass of 2×10⁻⁵ g was initiallydeposited onto a glassy carbon plate having the dimensions of 1centimeter by 0.5 centimeter by 0.04 centimeter so that the polymeroccupied the area of 0.5 centimeter by 0.5 centimeter on one side of theplate. The polymerization was accomplished by applying the constantpotential of +0.98 V (vs. a standard silver/silver chloride referenceelectrode) to the glassy carbon plate in the acetonitrile solutioncontaining 0.1 mol/L of tetraethylammonium tetrafluoroborate and 0.001mol/L of the monomer complex [Cu(CH₃O-Salen)]. The support with apolymer film on it was carefully rinsed with acetonitrile to remove anytraces of the monomer and supporting electrolyte and placed in the tubefurnace filled with high-purity nitrogen. The polymer was carbonized at600° C. for 3 hours. The final metal-carbon material contained 77 wt %of carbon and had a specific electrochemically-active surface area of2000 m²/g.

Example 2

The polymer synthesized following the same procedures as those inExample 1 was employed to prepare a metal-carbon material. The polymerwas carbonized at 500° C. for 3 hours. The final metal-carbon materialcontained 64 wt % of carbon and had a specific electrochemically-activesurface area of 1000 m²/g. The carbonization at a lower temperature thanthat employed in Example 1 results in incomplete carbonization. As aresult, the polymer lost redox conductivity before the carbon matrix wasfully formed, resulting in low electronic conductivity of the finalmetal-carbon material.

Example 3

The polymer synthesized following the same procedure as that in Example1 was employed to prepare a metal-carbon material. The polymer wascarbonized at 700° C. for 3 hours. The final metal-carbon materialcontained 77 wt % of carbon and had a specific electrochemically-activesurface area of 500 m²/g. The carbonization at a higher temperature thanthat employed in Example 1 lead to agglomeration of individualstructural elements, which resulted in low porosity of metal-carbonmaterial.

Example 4

The same procedures as that in Example 1 were followed with theexception that the precursor polymer film had the thickness of 0.4micrometers and mass of 1×10⁻⁵ g. The polymer was carbonized at 600° C.for 3 hours. After carbonization, the metal-carbon material contained 77wt % of carbon and had a specific electrochemically-active surface areaof 2000 m²/g. The comparison of these results with the results ofExample 1 demonstrates that the porosity of the metal-carbon materialdoes not depend on the thickness of the precursor polymer film, but israther defined by the initial distribution of structural elements(stacks) in the polymer.

Example 5

The same procedures as those in Example 1 were followed with theexception that the polymerization solution contained propylene carbonateinstead of acetonitrile, and the mass of the formed 0.8 micrometerprecursor polymer film was 7.5×10⁻⁶ g. After carbonization, themetal-carbon material contained 77 wt % of carbon and had a specificelectrochemically-active surface area of 750 m²/g. The larger solventmolecules (propylene carbonate) in the polymerization solution comparedto the solvent employed in Example 1 (acetonitrile) provide greaterdistances between the structural elements (stacks) of the precursorpolymer. This results in the increased pore size in the finalmetal-carbon material but a decreased amount of electroactive materialper square centimeter of the support, which is reflected in the lowvalue of a specific electrochemically-active surface area of thecomposite.

Example 6

A polymer film had a formula poly[Cu(CH₃O-Saltmen)] and a recurring unitwas

employed to prepare a metal-carbon material. The polymer film having thethickness of 0.8 micrometers and mass of 2.2×10⁻⁵ g was preliminarydeposited onto a glassy carbon plate having the dimensions 1 centimeterby 0.5 centimeter by 0.04 centimeter so that the polymer occupied thearea of 0.5 centimeter by 0.5 centimeter on one side of the plate. Thepolymerization was accomplished by applying the constant potential of+1.00 V (vs. a standard silver/silver chloride reference electrode) tothe glassy carbon plate in the acetonitrile solution containing 0.1mol/L of tetraethylammonium tetrafluoroborate and 0.001 mol/L of themonomer complex [Cu(CH₃O-Saltmen)]. The support with a polymer film onit was carefully rinsed with acetonitrile to remove any traces of themonomer and supporting electrolyte and placed in the tube furnace filledwith high-purity nitrogen. The polymer was carbonized at 600° C. for 3hours. The final metal-carbon material contained 81 wt % of carbon andhad a specific electrochemically-active surface area of 1200 m²/g. Therepulsive interactions between monomer fragments caused by the presenceof four additional methyl groups in the ligand portion of the monomerprovide greater distances between the structural elements (stacks) inthe precursor polymer with a formula poly[Cu(CH₃O-Saltmen)] as comparedwith the precursor polymer with a formula poly[Cu(CH₃O-Salen)] employedfor the synthesis of a metal-carbon material in Example 1. This resultsin the increased pore size in the final metal-carbon material but adecreased amount of electroactive material per square centimeter of thesupport, which is reflected in the low value of a specificelectrochemically-active surface area of the composite.

Example 7

A polymer film with a formula poly[Ni(Salen)] and a recurring unit of

was employed to prepare a metal-carbon material. The polymer film havingthe thickness of 0.8 micrometers and mass of 1.7×10⁻⁵ g was initiallydeposited onto the glassy carbon plate having the dimensions 1centimeter by 0.5 centimeter by 0.04 centimeter so that the polymeroccupied the area of 0.5 centimeter by 0.5 centimeter on one side of theplate. The polymerization was accomplished by applying the constantpotential of +1.00 V (vs. a standard silver/silver chloride referenceelectrode) to the glassy carbon plate in the acetonitrile solutioncontaining 0.1 mol/L of tetraethylammonium tetrafluoroborate and 0.001mol/L of the monomer complex [Ni(Salen)]. The support with a polymerfilm on it was carefully rinsed with acetonitrile to remove any tracesof the monomer and supporting electrolyte and placed in the tube furnacefilled with high-purity nitrogen. The polymer was carbonized at 600° C.for 3 hours. The final metal-carbon material contained 77 wt % of carbonand had a specific electrochemically-active surface area of 2500 m²/g.

Example 8

The same procedures as those in Example 7 were followed with theexception that the polymerization solution contained 0.1 mol/L oftetraethylammonium hexafluoro- phosphate instead of 0.1 mol/L oftetraethylammonium tetrafluoroborate, and the mass of the formed 0.8micrometer precursor polymer film was 1.2×10⁻⁵ g. After carbonization,the metal-carbon material contained 77 wt % of carbon and had a specificelectrochemically-active surface area of 1700 m²/g. The larger anions ofsupporting electrolyte (hexafluorophosphate ions) in the polymerizationsolution compared to the anions of the electrolyte employed in Example 7(tetrafluoroborate ions) provide greater distances between thestructural elements (stacks) of precursor polymer. This results in theincreased pore size in the final metal-carbon material but a decreasedamount of electroactive material per square centimeter of the support,which is reflected in the low value of a specificelectrochemically-active surface area of the composite.

Unless otherwise indicated, all numbers expressing lengths, widths,depths, or other dimensions, and so forth used in the specification andclaims are to be understood in all instances as indicating both theexact values as shown and as being modified by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the specification and attached claims are approximationsthat may vary depending upon the desired properties sought to beobtained. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques. Any specific value may vary by 20%.

The terms “a,” “an,” “the,” and similar referents used in the context ofdescribing the invention (especially in the context of the followingclaims) are to be construed to cover both the singular and the plural,unless otherwise indicated herein or clearly contradicted by context.All methods described herein can be performed in any suitable orderunless otherwise indicated herein or otherwise clearly contradicted bycontext. The use of any and all examples, or exemplary language (e.g.,“such as”) provided herein is intended merely to better illuminate theinvention and does not pose a limitation on the scope of any claim. Nolanguage in the specification should be construed as indicating anynon-claimed element essential to the practice of the invention.

Groupings of alternative elements or embodiments disclosed herein arenot to be construed as limitations. Each group member may be referred toand claimed individually or in any combination with other members of thegroup or other elements found herein. It is anticipated that one or moremembers of a group may be included in, or deleted from, a group forreasons of convenience and/or patentability. When any such inclusion ordeletion occurs, the specification is deemed to contain the group asmodified, thus fulfilling the written description of all Markush groupsused in the appended claims.

Certain embodiments are described herein, including the best mode knownto the inventor for carrying out the spirit of the present disclosure.Of course, variations on these described embodiments will becomeapparent to those of ordinary skill in the art upon reading theforegoing description. The inventor expects skilled artisans to employsuch variations as appropriate, and the inventor intends for theinvention to be practiced otherwise than specifically described herein.Accordingly, the claims include all modifications and equivalents of thesubject matter recited in the claims as permitted by applicable law.Moreover, any combination of the above-described elements in allpossible variations thereof is contemplated unless otherwise indicatedherein or otherwise clearly contradicted by context.

In closing, it is to be understood that the embodiments disclosed hereinare illustrative of the principles of the claims. Other modificationsthat may be employed are within the scope of the claims. Thus, by way ofexample, but not of limitation, alternative embodiments may be utilizedin accordance with the teachings herein. Accordingly, the claims are notlimited to embodiments precisely as shown and described.

What is claimed is:
 1. A method for creating a metal-carbon compositecomprising the steps of: a. providing a polymer Schiff base transitionmetal film complex precursor film having a chemical structure of theformula [M(Schiff)]_(n) and the recurring unit of the followingstructure:

wherein n is an integer between 2 and 50,000; M is a transition metalselected from the group consisting of nickel, palladium, platinum,cobalt, copper, and iron; Schiff is a tetradentate Schiff base ligandselected from the group consisting of Salen (residue ofbis(salicylaldehyde)-ethylenediamine), Saltmen (residue ofbis(salicylaldehyde)-tetramethylethylenediamine, and Salphen (residue ofbis-(salicylaldehyde)-o-phenylenediamine); R is a substituent in aSchiff base selected from the group consisting of H—;, andcarbon-containing substituents, preferably CH₃—, C₂H₅—, CH₃O—, C₂H₅O—;and Y is a bridge in a Schiff base and has the following structure:

or when the Schiff base is a Salen, a Saltmen and a Salphen,respectively, b. depositing the polymer Schiff base transition metalcomplex precursor film onto a support substrate; and c. heating thepolymer Schiff base transition metal complex precursor film and supportsubstrate in a furnace in an inert atmosphere.
 2. The method of claim 1wherein the support substrate is a glassy carbon plate.
 3. The method ofclaim 1 wherein the inert atmosphere is selected from one or more ofnitrogen, argon, and helium.
 4. The method of claim 1 wherein thepolymer Schiff base transition metal complex precursor film and supportsubstrate are heated between 500° C.-750° C. for 1-4 hours.
 5. Themethod of claim 4 wherein the polymer Schiff base transition metalcomplex precursor film and support substrate are heated from 550° C. to650° C.
 6. The method of claim 4 wherein the polymer Schiff basetransition metal complex precursor film and support substrate are heatedfrom 580° C. to 620° C.
 7. The method of claim 4 wherein the polymerSchiff base transition metal complex precursor film and supportsubstrate are heated for 2-3 hours.
 8. The method of claim 1 wherein thedeposition of the polymer Schiff base transition metal complex precursorfilm onto a support substrate comprises polymerization by application ofa constant potential to the substrate.
 9. The method of claim 8 whereinthe support substrate is a glassy carbon plate.
 10. The method of claim8 wherein the constant potential of +0.98V, as measured against astandard silver/silver chloride reference electrode, is applied to thesubstrate.
 11. The method of claim 8 wherein the polymerization of apolymer complex film occurs with the substrate positioned in a solutioncontaining tetraethylammonium tetrafluoroborate and the Schiff basemonomer complex.
 12. The method of claim 11 where a solvent of thesolution is acetonitrile.
 13. The method of claim 12 wherein the supportwith the polymer complex film on it is rinsed with acetonitrile prior tobeing placed in the furnace.
 14. The method of claim 11 where a solventof the solution is propylene carbonate.